java - 带有列表的 jsp 中的 NumberFormatException

Question

这个问题是我的应用程序遇到的另一个问题，描述为 here .我的模型(一个级别)有一个要求列表，其中包含两个字符串，一个 id 和一个名称。该模型如下所示:

public class Level {
private String name;
private int id;
private int points
private List<Requirement> requirements;
    ....
}

public class Requirement{
    private String name;
    private String id;
    ....
}

jsp 看起来像这样:

<div id="allRequirements">
    <c:forEach var="requirement" items="${RequirementList}">
         <div class="requirements">
             <input type="hidden" value="${requirement.id}" name="id"/>
             <h2><c:out value="${requirement.name}"/></h2>
         </div>
    </c:foreach>
</div>

<div id="requiredRequirements">
    <c:forEach var="requiredRequirement" items="${level.requirements}">
         <div class="requirements">
             <input type="hidden" value="${requiredRequirement.id}" name="id"/>
             <h2><c:out value="${requiredRequirement.name}"/></h2>
         </div>
    </c:foreach>
</div>

在我添加 requiredRequirements 循环之前，jsp 页面呈现得很好并且像一个魅力一样工作作为 int 的字符串。

有谁知道为什么第一个循环有效而第二个循环无效？

编辑:堆栈跟踪

java.lang.NumberFormatException: For input string: "id"
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
at java.lang.Integer.parseInt(Integer.java:447)
at java.lang.Integer.parseInt(Integer.java:497)
at javax.el.ListELResolver.coerce(ListELResolver.java:174)
at javax.el.ListELResolver.getValue(ListELResolver.java:52)
at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:67)
at org.apache.el.parser.AstValue.getValue(AstValue.java:169)
at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:189)
at org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:985)
at org.apache.jsp.WEB_002dINF.jsp.createOrEdit_005fLevelBody_jsp._jspx_meth_c_005fout_005f0(createOrEdit_005fLevelBody_jsp.java:648)
at org.apache.jsp.WEB_002dINF.jsp.createOrEdit_005fLevelBody_jsp._jspx_meth_c_005fforEach_005f1(createOrEdit_005fLevelBody_jsp.java:611)
at org.apache.jsp.WEB_002dINF.jsp.createOrEdit_005fLevelBody_jsp._jspService(createOrEdit_005fLevelBody_jsp.java:207)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:419)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:391)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:684)
at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:593)
at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:530)
at org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:927)
at org.apache.jasper.runtime.PageContextImpl.doInclude(PageContextImpl.java:684)
at org.apache.jasper.runtime.PageContextImpl.include(PageContextImpl.java:678)
at org.apache.tiles.jsp.context.JspTilesRequestContext.include(JspTilesRequestContext.java:103)
at org.apache.tiles.jsp.context.JspTilesRequestContext.dispatch(JspTilesRequestContext.java:96)
at org.apache.tiles.renderer.impl.UntypedAttributeRenderer.write(UntypedAttributeRenderer.java:61)
at org.apache.tiles.renderer.impl.AbstractBaseAttributeRenderer.render(AbstractBaseAttributeRenderer.java:103)
at org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:659)
at org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:337)
at org.apache.tiles.jsp.taglib.InsertAttributeTag.render(InsertAttributeTag.java:234)
at org.apache.tiles.jsp.taglib.InsertAttributeTag.render(InsertAttributeTag.java:211)
at org.apache.tiles.jsp.taglib.RenderTag.doEndTag(RenderTag.java:220)
at org.apache.jsp.WEB_002dINF.jsp.layout_jsp._jspx_meth_tiles_005finsertAttribute_005f3(layout_jsp.java:411)
at org.apache.jsp.WEB_002dINF.jsp.layout_jsp._jspService(layout_jsp.java:196)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:419)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:391)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:684)
at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:593)
at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:530)
at org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:927)
at org.apache.jasper.runtime.PageContextImpl.doInclude(PageContextImpl.java:684)
at org.apache.jasper.runtime.PageContextImpl.include(PageContextImpl.java:678)
at org.apache.tiles.jsp.context.JspTilesRequestContext.include(JspTilesRequestContext.java:103)
at org.apache.tiles.jsp.context.JspTilesRequestContext.dispatch(JspTilesRequestContext.java:96)
at org.apache.tiles.renderer.impl.TemplateAttributeRenderer.write(TemplateAttributeRenderer.java:44)
at org.apache.tiles.renderer.impl.AbstractBaseAttributeRenderer.render(AbstractBaseAttributeRenderer.java:103)
at org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:659)
at org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:678)
at org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:633)
at org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:322)
at org.apache.tiles.jsp.taglib.InsertDefinitionTag.renderContext(InsertDefinitionTag.java:66)
at org.apache.tiles.jsp.taglib.InsertTemplateTag.render(InsertTemplateTag.java:81)
at org.apache.tiles.jsp.taglib.RenderTag.doEndTag(RenderTag.java:220)
at org.apache.jsp.WEB_002dINF.jsp.createOrEdit_005fLevel_jsp._jspx_meth_tiles_005finsertDefinition_005f0(createOrEdit_005fLevel_jsp.java:87)
at org.apache.jsp.WEB_002dINF.jsp.createOrEdit_005fLevel_jsp._jspService(createOrEdit_005fLevel_jsp.java:60)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:419)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:391)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:684)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:471)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:402)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:329)
at org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:238)
at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:250)
at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1047)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:817)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:669)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:574)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:562)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:395)
at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:306)
at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:323)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1719)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)

谢谢

Answer 1

这意味着 ${requiredRequirement} 实际上是 List 的一个实例。在 EL 中，List 只能通过整数索引访问。这可能有两个原因:

1. 您的 Requirement 类实际上实现了 List 或扩展了它的子类之一。
2. ${level} 或 ${level.requirements} 实际上并没有引用您认为的代码。

作为快速调试，尝试简单地打印它们以检查它们的 toString() 方法是否返回您所期望的:

<p>Level: ${level}</p>
<p>Level requirements: ${level.requirements}</p>

在循环中

<p>Required requirement: ${requiredRequirement}</p>